Control valve system

ABSTRACT

A control valve system of a variable displacement swash plate type compressor for use in a heating and cooling air conditioner, which includes a throttling valve provided in a refrigerating circuit, a constant differential pressure valve arranged to open when a differential pressure between upstream and downstream pressures of the throttling valve reaches a predetermined value, thereby introducing compressor discharge gas to a crank chamber, external information detecting device for detecting external information such as cooling load or vehicle running state, and controller for determining an opening of the throttling valve based on the external information, and which is capable of performing a stable feedback control of the discharge capacity in a range from a small discharge capacity to a large discharge capacity, and suppressing the decrease in compressor efficiency at large discharge capacity.

CROSS-REFERENCE TO THE RELATED ART

[0001] This nonprovisional application claims priority under 35 U.S.C. §119(a) on patent application Ser. No. 2003-040445 filed in Japan on Feb.19, 2003, the entire contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a control valve system of avariable displacement swash plate type compressor for use in a heatingand cooling air conditioner.

[0004] 2. Description of the Related Art

[0005] Variable displacement swash plate type compressors are designedto adjust the pressure in the-crank chamber to thereby control thedischarge capacity. For example, in a variable displacement swash platetype compressor for use in a heating and cooling air conditioner, thepressure in the crank chamber is autonomously adjusted, so that adifferential pressure between predetermined two points in arefrigerating circuit approaches a target differential pressure that isdetermined based on external information supplied from an externalinformation detecting means. In other words, the differential pressurebetween these two points and, by extension, the discharge capacity, isfeedback controlled.

[0006] Japanese provisional patent publication no. 2001-107854 disclosesa control valve system of a variable capacity swash plate typecompressor for autonomously adjusting the pressure in the crank chamber.This control valve system is provided with a valve that is variable inopening and that has a valve body arranged to be urged in one directionby an electromagnetic force corresponding to a target differentialpressure between the predetermined two points in the refrigeratingcircuit and to be urged in the reverse direction by an actualdifferential pressure therebetween, the target differential pressurebeing determined based on external information supplied from externalinformation detecting means. The control valve system is furtherdesigned to introduce the discharge gas to the crank chamber through theaforementioned valve for autonomous adjustment of the pressure in thecrank chamber, in which adjustment the differential pressure between thetwo points and, by extension, the discharge capacity, is feedbackcontrolled, so that the differential pressure approaches the targetdifferential pressure.

[0007] The control valve system disclosed in JP-2001-107854 A requiresthat the differential pressure between the predetermined two points inthe refrigerating circuit be increased, in order to achieve a stablefeedback control of the differential pressure. To this end, for example,a restrictor must be provided between these two points.

[0008] However, the control valve system using a restrictor poses aproblem that, if the degree of restriction is made large, a pressureloss due to the restriction increases with the increasing dischargecapacity, resulting in a low compressor efficiency. On the other hand,if the degree of restriction is made small, the differential pressurebetween the two points decreases with the decrease in dischargecapacity, which makes a stable feedback control of the differentialpressure difficult, making it difficult to stably perform the feedbackcontrol of the discharge capacity.

SUMMARY OF THE INVENTION

[0009] The object of the present invention is to provide a control valvesystem of a variable capacity swash plate type compressor, which iscapable of performing a stable feedback control of the dischargecapacity in a range from a small discharge capacity to a large dischargecapacity, and capable of suppressing the decrease in compressorefficiency at large discharge capacity.

[0010] The present invention provides a control valve system of avariable displacement swash plate type compressor for use in a heatingand cooling air conditioner, which comprises a throttling valve providedin a refrigerating circuit; a constant differential pressure valvearranged to open when a differential pressure between upstream anddownstream pressures of the throttling valve reaches a predeterminedvalue, thereby introducing compressor discharge gas to a crank chamber;external information detecting means for detecting external informationsuch as cooling load or vehicle running state; and control means fordetermining an opening of the throttling valve based on the externalinformation.

[0011] In the control valve system of this invention, a target quantityof flow of refrigerant passing through the throttling valve and, byextension, a target discharge capacity of the compressor, is determinedbased on the pressure setting of the constant differential pressurevalve and the opening of the throttling valve which is in turndetermined based on the external information. The compressor dischargegas is introduced through the constant differential pressure valve,whereby the pressure in the crank chamber is autonomously adjusted.Thus, the differential pressure between the upstream and the downstreampressure of the throttling valve is feedback controlled so as toapproach the pressure setting of the constant differential pressurevalve, so that the quantity of flow of the refrigerant passing thethrottling valve is feedback controlled to approach the target quantityof flow. Consequently, the discharge capacity of the compressor isfeedback controlled to approach the target discharge capacity.

[0012] In case that the pressure setting of the constant differentialpressure valve is set to an appropriate value, it is possible to stablyfeedback control the differential pressure between the upstream and thedownstream pressure of the throttling valve in a range from a smalldischarge capacity to a large discharge capacity, thus achieving astable feedback control of the discharge capacity of the compressor.When the external information indicates the necessity of a largequantity of flow, the opening of the throttling valve is set to a largevalue to thereby make it possible to eliminate the possibility ofreduction in compressor efficiency due to the pressure loss at largedischarge capacity.

[0013] In this invention, it is preferable that the throttling valve bean electromagnetic valve and integrally mounted to the constantdifferential pressure valve.

[0014] The electromagnetic valve whose opening can be arbitrarily set bymeans of duty control is suitable to be used as the throttling valve.When the throttling valve is integrally mounted to the constantdifferential pressure vale, the resultant control valve system can becompact in size.

[0015] Preferably, the constant differential pressure valve is arrangedto introduce the compressor discharge gas on the upstream side of thethrottling valve into the crank chamber.

[0016] In an arrangement introducing the compressor discharge gas on thedownstream side of the throttling valve into the crank chamber, thedischarge gas cannot be introduced into the crank chamber when the airconditioner stops operating and hence the throttling valve is closed.This makes it impossible to reduce the discharge capacity when the airconditioner stops. Such drawback can be eliminated by the just-mentionedpreferred embodiment in which the discharge gas on the upstream side ofthe throttling valve is introduced into the crank chamber.

[0017] Preferably, the control valve system is provided with a cutoffvalve disposed on the downstream side of the throttling valve.

[0018] The provision of the cutoff valve can prevent high pressure gasin the refrigerating circuit from acting on the constant differentialpressure valve, when the air conditioner stops operating and thethrottling valve is closed. This ensures that the compressor dischargegas on the upstream side of the throttling valve is introduced to thecrank chamber, thus positively reducing the discharge capacity when theair conditioner stops.

[0019] Preferably, a discharge gas inflow chamber is formed on theupstream side of the throttling valve, and the compressor discharge gasin the discharge gas inflow chamber is introduced into the crankchamber. The discharge gas inflow chamber has an inlet thereof directedtangential to a wall surface of the discharge gas inflow chamber.

[0020] In case that the inlet of the discharge gas inflow chamber isdirected tangential to a wall surface of the discharge gas inflowchamber, the compressor discharge gas entering the discharge gas inflowchamber makes a circling motion therein, so that lubricating oilcontained in the compressor discharge gas is separated therefrom bymeans of centrifugal force. The separated lubricating oil is introducedthrough the constant differential pressure valve into the crank chambertogether with the compressor discharge gas, and thus the lubricating oilis positively supplied to the crank chamber.

[0021] Preferably, the discharge gas inflow chamber is formed with aplurality of inlets that are circumferentially spaced from one another.

[0022] With the discharge gas inflow chamber formed withcircumferentially spaced inlets, the compressor discharge gas makes acircling motion in the discharge gas inflow chamber, thus ensuring thatthe lubricating oil is separated from the compressor discharge gas.

[0023] Preferably, the throttling valve has a pressure receiving portionthat presses the throttling valve in a direction to be opened when itreceives a downstream side pressure.

[0024] The throttling valve having such a pressure receiving portiondecreases a pressing force due to the downstream side pressure acting onthe throttling valve. As a result, the accuracy in controlling theopening of the throttling Valve can be improved.

[0025] Preferably, the pressure receiving portion has the same area asthat of a downstream-side pressure receiving surface of the throttlingvalve.

[0026] In case that the pressure receiving portion and thedownstream-side pressure receiving surface of the throttling valve havethe same area, a pressing force due to the downstream side pressureacting to open the throttling valve balances a pressing force due to thedownstream side pressure acting to close the throttling valve. Thismakes it possible to carry out an accurate control of the throttlingvalve opening.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will become more fully understood from thedetailed description given herein below and the accompanying drawingswhich are given by way of illustration only, and thus, are notlimitative of the present invention, and wherein:

[0028]FIG. 1 is a block diagram showing a vehicle-mounted airconditioner equipped with a variable displacement swash plate typecompressor provided with a control valve system according to anembodiment of this invention;

[0029]FIG. 2 is a sectional view showing the control valve system whenthe air conditioner is in operation; and

[0030]FIG. 3 is a sectional view showing the control valve system whenthe air conditioner stops operating.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] In the following, a control valve system of a variabledisplacement swash plate type compressor according to one embodiment ofthis invention will be described.

[0032] As shown in FIG. 1, a vehicle-mounted air conditioner A isconstituted by a variable displacement swash plate type compressor 1, acondenser 2, an expansion valve 3, and an evaporator 4. The airconditioner A is also provided with a damper 5 for switching airpassages between fresh air introduction and inside air circulation, ablower 6, and an air conditioner operation panel 7.

[0033] The air conditioner operation panel 7 is equipped with an on-offswitch 7 a and a temperature setter 7 b for the air conditioner A, whichare operable by the driver or a front seat passenger. A temperaturesensor 4 a for detecting an air temperature in the compartment isprovided near the evaporator 4, and various sensors for detecting avehicle running state, such as vehicle speed sensor, engine rotationspeed sensor, throttle opening sensor, etc., are provided in thevehicle, not shown. The on-off switch 7 a, temperature setter 7 b,temperature sensor 4 a, and various sensors for detecting a vehiclerunning state cooperate with one another to form an external informationdetecting device 8.

[0034] The variable displacement swash plate type compressor 1 comprisesa main shaft (not shown) coupled to the automotive engine (not shown)without using a clutch, a swash plate (not shown) mounted to the mainshaft so as not to be relatively rotatable but to be variable ininclination angle, a piston (not shown), engaged with the swash platethrough a shoe, for a linear reciprocal motion with the rotation of theswash plate, a cylinder bore 1 a in which the piston is received forsliding motion, a discharge chamber 1 b communicating with the cylinderbore 1 a through a discharge valve, a crank chamber 1 c accommodatingthe main shaft and the swash plate, and a suction chamber 1 dcommunicating with the cylinder bore 1 a through a suction valve. Thecrank chamber 1 c is communicated with the suction chamber 1 d throughan orifice hole 1 e.

[0035] The discharge chamber 1 b, the condenser 2, the expansion valve3, the evaporator 4, and the suction chamber 1 d are connected with oneanother by means of a refrigerating circuit 9.

[0036] There is provided a control valve system 10 for controlling thedischarge capacity of the compressor 1. The control valve system 10comprises a throttling valve 11 disposed in the refrigerating circuit 9near the discharge chamber 1 b, a constant differential pressure valve12 adapted to open to introduce compressor discharge gas into the crankchamber 1 c when the differential pressure between an upstream pressureP″ and a downstream pressure P′ of the throttling valve 11 reaches apredetermined value, the aforementioned external information detectingdevice 8, a controller 13 for determining the opening of the throttlingvalve 11 based on external information supplied from the externalinformation detecting device 8, and a driving circuit 14 for thethrottling valve 11.

[0037] Referring to FIG. 2, the throttling valve 11 and the constantdifferential pressure valve 12 will be described in detail.

[0038] The throttling valve 11 comprises a coil 11 a, a stationary ironcore 11 b, a movable iron core 11 c, a rod 11 d fixed to the movablecore 11 c, a valve body 11 e fixed to an end portion of the rod 11 d,and a valve seat 11 f, the coil 11 a being connected to the drivingcircuit 14 through wires, not shown.

[0039] On the upstream side of the valve body 11 e, an annular dischargegas inflow chamber 11 d is provided coaxially with the rod 11. Thedischarge gas inflow chamber 11 g has an outer peripheral wall formedwith a plurality of discharge gas inlets 11 g′ so as to becircumferentially spaced from one another. These discharge gas inlets 11g′ are directed perpendicularly to the center axis of the discharge gasinflow chamber 11 g and tangential to the inner peripheral surface ofthe outer peripheral wall of the chamber 11 g. The discharge gas inlets11 g′ are communicated through the refrigerating circuit 9 to thedischarge chamber 1 b of the compressor 1.

[0040] The discharge gas inflow chamber 11 g is communicated with achamber 11 h that is formed on the upstream side of the valve body 11 eso as to be adjacent to the valve body 11 e. A chamber 11 i is formed onthe downstream side of the valve body lie so as to be adjacent thereto,and is communicated with the chamber 11 h.

[0041] A gas passage 11 j extending from the chamber 11 i iscommunicated with a chamber 11 k formed behind the chamber 11 h. Amovable plate 11 m, having a first pressure receiving surface 11 m′disposed in contact with the chamber 11 k, is fixed to the rod 11 d. Thefirst pressure receiving surface 11 m′ has its area that is the same asthat of a downstream-side pressure receiving surface 11 e′ of the valvebody lie. A spring 11 n that urges the valve body 11 e toward the valveseat 11 f is disposed in contact with a second pressure receivingsurface 11 m″ that is disposed on the side opposite the first pressurereceiving surface 11 m′. The second pressure receiving surface 11 m″ isadjacent to the chamber 11 h via a space in which the spring 11 n isreceived. The area of the second pressure receiving surface 11 m″ is setto a value that is the same as the area of the upstream-side pressurereceiving surface 11 e″ of the valve 11 e. As a result, an urging force,due to the downstream-side pressure P′ of the throttling valve 11applied to the first pressure receiving surface 11 m″ of the movableplate 11 m, acting to move the valve body 11 e in the direction awayfrom the valve seat 11 f balances an urging force, due to thedownstream-side pressure P′ of the throttling valve 11 applied to thesecond pressure receiving surface 11 e′, acting to move the valve body11 e in the direction toward the valve seat 11 f. Also, an urging force,due to the upstream-side pressure P″ of the throttling valve 11 appliedto the second pressure receiving surface 11 m′ of the movable plate 11m, acting to move the valve body 11 e in the direction toward the valveseat 11 f balances an urging force, due to the upstream-side pressure P″of the throttling valve 11 applied to the upstream-side pressurereceiving surface 11 e″ of the valve body 11 e, acting to move the valvebody 11 e in the direction away from the valve seat 11 f.

[0042] On the downstream side of the throttling valve 11, a chamber 11 pis provided to be adjacent to and communicated with the chamber 11 i.The chamber 11 p has its outer peripheral wall formed with a dischargegas outlet 11 p′ that is connected through the refrigerating circuit 9to the condenser 2 of the air conditioner A.

[0043] The cutoff valve 15 is disposed in the chamber 11 p and comprisesa valve body 15 a, a valve seat 15 b, and a spring 15 c that urges thevalve body 15 a toward the valve seat 15 b.

[0044] The constant differential pressure valve 12 comprises a rod 12 a,a valve body 12 b fixed to the vicinity of one end of the rod 12 a, amovable plate 12 c fixed to another end of the rod 12 a, a valve seat 12d, and a spring 12 e disposed in contact with the movable plate 12 c andurging the valve body 12 toward the valve seat 12 d.

[0045] On the upstream side and the downstream side of the valve body 12b, chambers 12 f, 12 g are formed adjacent to the valve body 12 b,respectively. The chamber 12 f is in communication with the dischargegas inflow chamber 11 g of the throttling valve 11 through a gas passage12 h. The chamber 12 f has its outer peripheral wall formed with adischarge gas outlet 12 g′ that is in communication with the crankchamber 1 c of the compressor 1 through a passage 12 i.

[0046] A chamber 12 j is formed that accommodates the movable plate 12 cand the spring 12 e. A first portion 12 j′ of the chamber 12 faccommodating the spring 12 e is communicated through a gas passage 12 kwith the chamber 11 i of the throttling valve 11, whereas a secondportion 12 j″ thereof, facing the first portion 12 j′ with the movableplate 12 c interposed between these portions, is communicated through agas passage 12 m with the chamber 12 f.

[0047] To the-first portion 12 j′ of the chamber 12 j, thedownstream-side pressure P′ of the throttling valve 11 is introducedthrough the chamber 11 i and the gas passage 12 k, whereas theupstream-side pressure P″ of the throttling valve 11 is introduced intothe second portion 12 j″ of the chamber 12 j through the discharge gasinflow chamber 11 g, the gas passage 12 h, the chamber 12 f, and the gaspassage 12 m.

[0048] The pressure setting of the constant differential pressure valve12 is fixed at AP. More specifically, the spring constant of the spring12 e is set such that, when the differential pressure between theupstream-side pressure P″ of the throttling valve 11 applied from thesecond portion 12 j″ of the chamber 121 to the movable plate 12 c andthe downstream-side pressure P′ of the throttling valve 11 applied fromthe first portion 12 j′ of the chamber 12 j to the movable plate 12 c isless than the predetermined value AP, the valve body 12 b is caused toabut against the valve seat 12 d so that the communication between thechambers 12 f, 12 g is prohibited. On the other hand, when thedifferential pressure exceeds the predetermined value AP, the valve body12 b is allowed to move in the direction away from the valve seat 12 dby a distance corresponding to the differential pressure. When thedifferential pressure is equal to the predetermined value AP, the valvebody 12 b is allowed to move in the direction away from the valve seat12 d by a predetermined distance.

[0049] The throttling valve 11, the constant differential pressure valve12, and the cutoff valve 15 are assembled into one piece.

[0050] In the following, the operation of the control valve system 10having the above-mentioned construction will be described.

[0051] The main shaft, not shown, of the variable displacement swashplate type compressor 1 always rotates by being driven by the automotiveengine, not shown.

[0052] When the air conditioner A is in operation, the controller 13determines the discharge capacity Q of the compressor 1 and by extensionthe target quantity Q of flow of the compressor discharge gas, which isrefrigerating gas flowing through the refrigerating circuit 9, on thebasis of external information supplied from the external informationdetecting device 8. The controller 13 also determines the preset openingΘ of the throttling valve 11 from the target quantity Q of flow and thepressure setting AP of the constant differential pressure valve 12.Further, the controller 13 operates the driving circuit 14 to carry outa duty control of electric power supplied to the coil 11 a of thethrottling valve 11. An electromagnetic force is exerted between themagnetized movable and stationary cores 11 c, 11 b, whereby the movablecore 11 c is caused to move against the urging force of the spring 11 n.Thus, the valve body 11 e moves in the direction away from the valveseat 11 f, so that the opening of the throttling valve 11 is made equalto the preset opening Θ.

[0053] The electromagnetic valve constituted by the coil 11 a,stationary core 11 b, movable core 11 c, rod 11 d, valve body 11 e andvalve seat 11 f can have the opening that can be arbitrarily set bymeans of the duty control. Hence, the electromagnetic valve is suitablefor use as the throttling valve 11. An urging force, due to thedownstream-side pressure P′ applied to the first pressure receivingsurface 11 m′ of the movable plate 11 m, acting to move the valve body11 e in the direction away from the valve seat 11 f balances an urgingforce, due to the downstream-side pressure P′ of the throttling valve 11applied to the downstream-side pressure receiving surface 11 e′ of thevalve body 11 e, acting to move the valve body 11 e in the directiontoward the valve seat 11 f. In addition, an urging force, due to theupstream-side pressure P″ of the throttling valve 11 applied to thesecond pressure receiving surface 11 m″ of the movable plate 11 m,acting to move the valve body 11 e in the direction toward the valveseat 11 f balances an urging force, due to the upstream-side pressure P″of the throttling valve 11 applied to the upstream-side pressurereceiving surface 11 e″ of the valve body 11 e, acting to move the valvebody 11 e in the direction away from the valve seat 11 f. Therefore, theopening of the throttling valve 11 is determined depending solely on therelation in size between the electromagnetic force applied from thestationary core 11 b to the movable core 11 c and the urging force ofthe spring 11 n. This makes it possible to accurately control theopening of the throttling valve 11 by means of the duty control ofelectric power supplied to the coil 11 a.

[0054] The compressor discharge gas flows from the discharge chamber 1b, through the refrigerating circuit 9 and the discharge gas inlet 11g′, into the discharge gas inflow chamber 11 g, and flows into thechamber 11 h. Then, the discharge gas passes through a gap between thevalve body 11 e and the valve seat 11 f to enter the chamber 11 i, andflows into the chamber 11 p. When receiving the dynamic pressure of thecompressor discharge gas entering the chamber lip, the valve body 15 aof the cutoff valve 15 is kept apart from the valve seat 15 against theurging force of the spring 15 c. In other words, the cutoff valve 15 iskept open. Thus, the compressor discharge gas flowing into the chamberlip flows to the condenser 2 through the discharge gas outlet 11 p′ andthe refrigerating circuit 9.

[0055] When the differential pressure between the upstream-side pressureP″ and the downstream-side pressure P′ of the throttling valve 11 isless than the predetermined value ΔP, the valve body 12 b is caused toabut against the valve seat 12 d to close the constant differentialpressure valve 12, so that the communication between the chambers 12 f,12 g is prohibited, and the compressor discharge gas in the dischargegas inflow chamber 11 g is prevented from flowing into the crank chamber1 c. The gas in the crank chamber 1 c is discharged to the suctionchamber 1 d through the orifice hole 1 e, resulting in a reduction inthe internal pressure in the crank chamber 1 c. As a consequence, theinclination angle of the swash plate, not shown, increases to increasethe discharge capacity of the variable displacement swash plate typecompressor 1, whereby the quantity of flow of the compressor dischargegas passing through the throttling valve 11 is increased to result inthe increased differential pressure between the upstream-side pressureP″ and the downstream-side pressure P′ of the throttling valve 11.

[0056] When the differential pressure between the upstream-side pressureP″ and the downstream-side pressure P′ of the throttling valve 11exceeds the predetermined value ΔP, the valve body 12 b is apart fromthe valve seat 12 d by a distance corresponding to the differentialpressure, to open the constant differential pressure valve 12. Thus, thecompressor discharge gas whose quantity of flow corresponds to thedistance between the valve body 12 b and the valve seat 12 d flows fromthe discharge gas inflow chamber 11 g to the crank chamber 1 c throughthe gas passage 12 h, chambers 12 f, 12 g, discharge gas outlet 12 g′and passage 12 i. Hence, the quantity of flow of the compressordischarge gas flowing into the crank chamber 1 c is greater than thequantity of flow of the gas discharged from the crank chamber 1 c to thesuction chamber 1 d, resulting in the increase in internal pressure inthe crank chamber 1 c. As the internal pressure in the crank chamber 1 cincreases, the inclination angle of the swash plate, not shown,decreases. This results in the decrease in discharge capacity of thecompressor 1, so that the quantity of flow of the compressor dischargegas passing through the throttling valve 11 decreases, thus decreasingthe differential pressure between the upstream-side pressure P″ and thedownstream-side pressure P′ of the throttling valve 11.

[0057] When the differential pressure between the upstream-side pressureP″ and the downstream-side pressure P′ of the throttling valve 11 isequal to the predetermined value ΔP, the valve body 12 b is apart fromthe valve seat 12 d by the predetermined distance, thus opening theconstant differential pressure valve 12. The quantity of flow of thecompressor discharge gas, corresponding to the distance between thevalve body 12 b and the valve seat 12 d, flows from the discharge gasinflow chamber 11 g into the crank chamber 1 c though the gas passage 12h, chambers 12 f, 12 g, gas outlet 12 g′ and passage 12 i. Equilibriumis established between the quantity of flow of the compressor dischargegas flowing into the crank chamber 1 c and that of the gas dischargedfrom the crank chamber 1 c to the suction chamber 1 d. Thus, theinternal pressure in the crank chamber 1 c does not increase anddecrease, and the inclination angle of the swash plate, not shown, doesnot increase and decrease. Consequently, the discharge capacity of thevariable displacement swash type compressor 1 does not increase anddecrease, and the quantity of flow of the discharge gas passing throughthe throttling valve 11 does not increase and decrease, so that thedifferential pressure between the upstream-side pressure P″ and thedownstream-side pressure P′ of the throttling valve does not increaseand decrease.

[0058] The introduction of the compressor discharge gas to the crankchamber 1 c and the prohibition of the introduction are autonomouslyrepeated to autonomously adjust the internal pressure in the crankchamber 1 c, whereby the differential pressure between the upstream-sidepressure P″ and the downstream-side pressure P′ of the throttling valve11 is feedback controlled so as to approach the pressure setting ΔP ofthe constant differential pressure valve 12. Thus, the quantity of flowof the compressor discharge gas passing through the throttling valve 11is feedback controlled to approach the target quantity Q of flow, andthus the discharge capacity of the compressor 1 is feedback controlledto approach the target value Q. As a result of the feedback control, ifthe differential pressure between the upstream-side pressure P″ and thedownstream-side pressure P′ of the throttling valve 11 is equal to thepressure setting ΔP of the constant differential pressure valve 12, thequantity of flow of the compressor discharge gas passing through thethrottling valve 11 and determined based on the differential pressure ΔPand the preset opening Θ of the throttling valve 11 becomes equal to thetarget quantity Q of flow. Thus, the discharge capacity of thecompressor 1 becomes equal to the target value Q, and the quantity offlow of the refrigerant flowing through the refrigerating circuit 9becomes equal to the target quantity of flow, Q. As shown by bold arrowin FIG. 1, appropriate air conditioning that corresponds to the externalinformation can be achieved when the target flow quantity Q of therefrigerant flows through the condenser 2, the expanding valve 3, andthe evaporator 4.

[0059] By using the constant differential pressure valve 12 whosepressure setting ΔP is set to the appropriate value, the differentialpressure between the upstream-side pressure P″ and the downstream-sidepressure P′ of the throttling valve 11 can be stably feedback controlledin a range from a small discharge capacity to a large dischargecapacity, making it possible to achieve a stable feedback control of theflow quantity of the compressor discharge gas passing through thethrottling valve 11, and by extension, the discharge capacity of thecompressor 1. When the necessity of a large flow quantity is indicatedby the external information detected by the external informationdetecting device 8, the opening of the throttling valve 11 is set to belarge, and accordingly, there is no fear of the efficiency of thecompressor 1 being lowered due to pressure loss at large dischargecapacity.

[0060] When the on-off switch 7 a is turned off and hence the airconditioner A stops operating, the controller 13 operates the drivingcircuit 14 so as to stop the power supply to the coil 11 a.

[0061] Thus, the application of electromagnetic force from thestationary iron core 11 b to the movable iron core 11 c is prevented, sothat the movable core 11 c receiving the urging force of the spring 11 nis moved in the direction away from the stationary core 11 b, wherebythe valve body 11 e is moved in the direction toward the valve seat 11 fand abuts against the valve seat 11 f. As a result, as shown in FIG. 3,the throttling valve 11 is closed, so that the compressor discharge gasis prevented from flowing from the chamber 11 i into the chamber 11 iand from the chamber 11 i into the chamber 11 p, whereby the flow ofrefrigerant in the refrigerating circuit 9 is prevented.

[0062] When the air conditioner A stops, the expanding valve 3 isclosed, and hence the gas passage between the chamber 11 i and theexpanding valve 3 is spatially closed. Accordingly, the compressordischarge gas no longer flows into the first portion 12 j′ of thechamber 121. Since the compressor 1 is in operation, the compressordischarge gas continues to flow into the second portion 12 j″ of thechamber 12 j. As a result, the differential pressure between the gaspressure applied from the second portion 12 j″ of the chamber 12 to themovable plate 12 c and the gas pressure applied from the first portion12 j′ of the chamber 12 greatly exceeds the pressure setting ΔP of theconstant differential pressure valve 12, whereby the valve 12 is fullyopened. Consequently, the compressor discharge gas flows into thethrottling valve 11 and flows through the passage 12 i into the crankchamber 1 c, and the internal pressure in the crank chamber 1 cincreases to decrease the inclination angle of the swash plate. As aresult, the discharge capacity of the compressor 1 decreases to aminimum value, thus suppressing the waste of energy produced by theautomotive engine. Even if the constant differential pressure valve 12is open when the air conditioner A is rendered inoperative and thethrottling valve 11 is closed, the compressor discharge gas flowsthrough the passage 12 i into the crank chamber 1 and continues to flowinto the second portion 12 j″ of the chamber 12 j. Thus, the constantdifferential pressure valve 12 is fully opened.

[0063] After flowing from the throttling valve 12 into the crank chamber1 c through the constant differential pressure valve 12, the dischargegas flows through the orifice hole 1 e into the suction chamber 1 d.Subsequently, as shown by bold double arrow in FIG. 1, the discharge gasis sucked from the suction chamber 1 d into the cylinder bore 1 a of thecompressor 1 which is kept in operation, is then discharged from thecylinder bore 1 a to the discharge chamber 1 b, and is returned to thethrottling valve 11.

[0064] When the throttling valve 11 is closed, the discharge gas flowingfrom the chamber 11 i into the chamber 11 p stops applying a dynamicpressure onto the valve body 15 a. The valve body 15 a is moved towardthe valve seat 15 b by means of the urging force of the spring 15 c, andabuts against the valve seat 15 b, whereby the cutoff valve 15 isclosed.

[0065] Since the compressor discharge gas flowing into the throttlingvalve 11 is recirculated to the valve 11 by way of the suction chamber 1d, the gas pressure in the discharge gas inflow chamber 11 g rapidlydecreases to the vicinity of the suction pressure. In case that thecutoff valve 15 is not closed with the closure of the throttling valve11, the pressure setting ΔP of the constant differential pressure valve12 is not exceeded by the differential pressure between the internalpressure in the second portion 12 j″ of the chamber 12 j that decreaseswith the decreasing gas pressure in the discharge gas inflow chamber 11g and the internal pressure in the first portion 12 j′ of the chamber 12j that cooperates with the gas passage extending between the chamber 11i and the expansion valve 3 to form a closed space. Thus, the constantdifferential pressure valve 12 is closed. As a result, the compressordischarge gas is impeded from flowing into the crank chamber 1 c toinhibit the rise in the internal pressure in the crank chamber 1 c,whereby the inclination angle of the swash plate is inhibited fromdecreasing, and the minimization of the discharge capacity of thevariable displacement swash plate type compressor 1 is inhibited.Consequently, there occurs a drawback that the suppression of waste ofenergy produced by the automotive engine can be impaired. In case thatthe cutoff valve 15 is closed with the closure of the throttling valve11, on the other hand, the movable plate 12 c is prevented from movingup to a position where it closes the constant differential pressurevalve 12, even if the pressure setting ΔP of the valve 12 is notexceeded by the differential pressure between the internal pressures inthe first and second portions 12 j′, 12 j″ of the chamber 12 j, becausethe volume of a closed space is small that is defined by the chamber 11i, the discharge gas passage 12 k, and the first portion 12 j′ of thechamber 12 i. When the movable plate 12 c moves in the direction toclose the constant differential pressure valve 12, the volume of thefirst portion 12 j′ of the chamber 12 j increases, and the volume of theclosed space defined by the chamber 11 i, the discharge gas passage 12k, and the first portion 12 j′ of the chamber 12 j increases. Since thevolume of the closed space is small, a slight increase in the volume ofthe first portion 12 j′ of the chamber 12 j results in a large rate ofvolume increase of the closed space, so that the internal pressure inthe closed space greatly decreases. As a consequence, the differentialpressure between the internal pressures in the first and second portions12 j′, 12 j″ of the chamber 12 j increases to exceed the pressuresetting ΔP of the constant differential pressure valve 12, whereby themovable plate 12 c is pushed back in the direction to open the valve 12.Since the valve 12 is kept open, the compressor discharge gas flows intothe crank chamber 1 c, and the discharge capacity of the compressor 1 isminimized, whereby the waste of energy produced by the automotive engineis suppressed.

[0066] The throttling valve 11, the constant differential pressure valve12, and the cutoff valve 15 are assembled into one piece, andaccordingly, the control valve system 10 is made compact.

[0067] The compressor discharge gas on the upstream side of thethrottling valve 11 must be introduced into the crank chamber 1 c forthe reason that, if the discharge gas on the downstream side of thethrottling valve 11 is introduced to the crank chamber 11 c, thedischarge gas cannot be introduced to the crank chamber 11 c, making itimpossible to reduce the discharge capacity of the compressor 1 when theair conditioner A stops operating and the throttling valve 11 is closed.

[0068] Since the discharge gas inlets 11 g′ of the discharge gas inflowchamber 11 g are directed tangential to the inner wall surface of thechamber 11 g, the compressor discharge gas entering the chamber 11 gmakes a circling motion therein, so that lubricating oil contained inthe discharge gas is separated therefrom by means of centrifugal force.The separated lubricating oil is introduced through the constantdifferential pressure valve 12 into the crank chamber 1 c together withthe discharge gas. Thus, the lubricating oil is positively supplied tothe crank chamber 1 c.

[0069] The discharge gas inlets 11 g′ of the discharge gas inflowchamber 11 g are circumferentially spaced from one another, andtherefore, the compressor discharge gas makes a circling motion in thechamber 11 g, which ensures that the lubricating oil is separated fromthe discharge gas.

[0070] In the above, the control valve system 10 according to oneembodiment of this invention has been described. This invention is notlimited to the foregoing embodiment, and may be modified variously.

[0071] For example, the first pressure receiving surface 11 m′ of themovable plate 11 m is not essentially required to have the same area asthat of the downstream-side pressure receiving surface 11 e′ of thevalve body lie. Also, the second pressure receiving surface 11 m″ of themovable plate 11 m may not have the same area as that of theupstream-side pressure receiving surface 11 e″ of the valve body lie. Aslong as the movable plate 11 m is formed with the first and secondpressure receiving surfaces 11 m′, 11 m″ to which the downstream sidepressure and the upstream side pressure of the throttling valve 11 areapplied, respectively, pressing forces acting on the throttling valve 11due to the upstream side pressure and the downstream side pressure ofthe throttle valve 11 are decreased, thus improving the accuracy ofcontrol of the opening of the throttling valve

What is claimed is:
 1. A control valve system of a variable displacementswash plate type compressor for use in a heating and cooling airconditioner, comprising: a throttling valve provided in a refrigeratingcircuit; a constant differential pressure valve arranged to open when adifferential pressure between upstream and downstream pressures of thethrottling valve reaches a predetermined value, thereby introducingcompressor discharge gas to a crank chamber; external informationdetecting means for detecting external information such as cooling loador vehicle running state; and control means for determining an openingof the throttling valve based on the external information.
 2. Thecontrol valve system according to claim 1, wherein said throttling valveis an electromagnetic valve and integrally mounted to said constantdifferential pressure valve.
 3. The control valve system according toclaim 1 or 2, wherein said constant differential pressure valve isarranged to introduce the compressor discharge gas on the upstream sideof said throttling valve into the crank chamber.
 4. The control valvesystem according to claim 3, further comprising a cutoff valve disposedon the downstream side of said throttling valve.
 5. The control valvesystem according to claim 3 or 4, wherein a discharge gas inflow chamberis formed on the upstream side of said throttling valve, the compressordischarge gas in said discharge gas inflow chamber is introduced intothe crank chamber, and said discharge gas inflow chamber has an inletthereof directed tangential to a wall surface of the discharge gasinflow chamber.
 6. The control valve system according to claim 5,wherein said discharge gas inflow chamber is formed with a plurality ofinlets that are circumferentially spaced from one another.
 7. Thecontrol valve system according to claim 1 or 2, wherein said throttlingvalve has a pressure receiving portion that presses said throttlingvalve in a direction to be opened when it receives a downstream sidepressure.
 8. The control valve system according to claim 7, wherein thepressure receiving portion has the same area as that of adownstream-side pressure receiving surface of said throttling valve.